1. H. Attouch, C. Picard, Asymptotic analysis of variational problems with constraints of obstacle type, J. Funct. Anal. 15 (1983), 329–386.
2. H. Brézis, F. E. Browder, Some properties of higher order Sobolev spaces, J. Math, pures et appl. 61 (1982), 245–259.
3. L. Carbone, F. Colombini, On convergence of functional with unilateral constraints, J. Math, pures et appl. 59 (1980), 465–500.
4. G. Choquet, Potentiels sur un ensemble de capacité nulle. Suites de potentiels, C.R. Acad. Sc. Paris 244 (1957), 1707–1710.
5. D. Cioranescu, L. Hedberg, F. Murat, Le bilaplacien et le tapis du fakir J (1983), non publié.